Proximity Coupled Cavity Backed Patch Antenna for Long Range UHF RFID Tag

A novel proximity coupled cavity backed patch antenna for long range Radio Frequency Identilication (RFID) tag is proposed in this communication. The RFID tag may sustain fair amount of impact or scratch, since the circuitry is protected inside the metal cavity. The novel feeding structure incorporates a full π network for line impedance tuning. A patch structure with two shorting joints is also proposed, where the shorting joints not only offer mechanical support for the patch but may also serve as a way to tune the resonant frequency of the antenna. A prototype was fabricated and achieved a gain of 5.7 dBi, which gives it a reading range of up to 23 m.